JPS63290936A - Device and method of measuring thickness of lubricating film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lubricating film thickness measuring device and method;
More particularly, the present invention relates to an apparatus and method for capacitively measuring the thickness of elastohydrodynamic coatings in rolling member bearings.

[Prior art]

Particularly in lubricating devices used in gyroscope applications, it is desirable to minimize drag torque and maintain constant characteristics over long periods of time. In order to increase the life of lubricated parts, it has been necessary to inspect lubricating devices that supply a constant amount of lubricant over a long period of time. In bearings, excess oil has been shown to result in high drag torques due to excessive viscous drag, reduced stability of the rolling element retainer (cage), and increased generated vibrations. It is important to supply the correct amount of oil between the friction surfaces. In addition, if there is insufficient oil, the elastohydrodynamic film will be thin and the resulting frictional resistance will be high, leading to premature wear and early failure of the bearing.

In systems that supply oil to operating rolling member bearings using an active control device, known as an active independent lubrication system, which monitors the oil supply and injects oil as needed. , the working elastohydrodynamics (E
) (D) It is necessary to know how thick the film is. The EHD film is a film of lubricating oil formed between the rolling member and the raceway of the rolling part side bearing in operation. In addition to other variations in bearing mechanics as a function of changes in coating thickness, measurements of EHD coating thickness must be made accurately in an absolute sense so that minimum lubrication requirements can be established. No. However, in attempts using common coating thickness measurement methods, the data are irregular and
Moreover, it was non-repetitive and not completely satisfactory.

One common method for determining the thickness of an EHD coating is to measure the resistance of a working rolling bearing. When a constant current is supplied from the inner race to the outer race of a rolling member bearing, since the lubricating oil has a high dielectric constant, the voltage across the bearing will vary as a function of the resistance, and the three resistors will be EHD. Varies as a function of coating thickness.

In an operating bearing, a film of lubricant forms between the rolling member and the raceway. The dielectric constant of oil is high, so even a thin film produces a very high resistance. However, since the surfaces of the rolling member and the raceway are not perfect, the surface roughness periodically approaches each other, and when they approach each other in this way, the resistance Fi is always low between the tracks.

This effect significantly reduces the signal-to-noise ratio in the field of detailed coatings, which requires the most precise data.

The main problem with using the working bearing resistance measurement method to determine EHD coating thickness is that the resistance path between the two races is affected by ball mechanics and the microscopic surface treatment of the ball and race. Yes, it changes over time. These resistance changes cause the noise level of the cage to be very high and also make it difficult to obtain an average resistance value that is related to the film thickness.

Another problem with the resistance measurement method is that the conductivity of oil is very low, so when a film forms, the resistance is very high. This means that it will never change. Therefore, this resistance measurement method is not suitable for use only when the coating thickness is sufficient, that is, when there is no contact between the ball and the race.

As described above, the conventional technology has several limitations. Therefore, other methods need to be provided to overcome these limitations.

[Summary of the invention]

The present invention provides a lubricant film thickness measuring device that includes a rolling member having a rotatable shaft extending into a housing. An electrically insulated inner race is rotatably engaged to a shaft within the housing, and an electrically insulated fixed outer race is also disposed within the housing and forms a raceway with the inner race. A rolling member is movably attached to the raceway. moreover,
A device is installed to measure the capacitance of the bearing.

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the drawings are for the purpose of helping understanding the present invention, and the present invention is not limited thereto.

〔Example〕

In FIG. 1, a double row ball bearing 10 is held within a cartridge or housing 12.

The first bearing set 14 and the second bearing set 16 have an external driven shaft 18 extending therethrough. Since the bearing cera) 14i6 are similar, only one will be explained. The shaft 18 is
It extends through the housing 12 and is fixed at a portion 13 to drive the inner race 20 in rotation.

A plurality of rolling members, such as ball bearings 22, rotate within a raceway formed between rotating inner race 20 and stationary outer race 26. Alternatively, the shaft 18 and the inner race 20 may be fixed, and the outer race 26 may rotate relative thereto.

The bearing sets 14 , 16 are fixed side by side within the housing 12 between the seven flange 28 and the retaining ring 30 .

The capacitance between the inner and outer races of a rotating rolling member bearing is an exponential function of the EHD coating thickness. The total capacitance can be formed as a parallel and series capacitor network where the lubricant is dielectric and the rolling member and raceway act as conductive grates. One of the advantages of using capacitance rather than resistance as a detection parameter is that the effects of surface roughness and bumps are very small. If roughness or bumps reduce the minimum distance between surfaces, the resistance will drop sharply and cause noise spikes. Since capacitance is a function of surface area as well as distance between surfaces, the change in capacitance due to similar roughness is much smaller.

To implement this method, the bearing must be electrically insulated. FIG. 1 shows an embodiment of a device for measuring coating thickness using capacitive technology. Ball bearing 22 is electrically isolated from housing 12 and shaft 18 by insulator 32 . The high frequency signal connects the inner and outer wires 34.36
are supplied to the inner race and outer race 20.26, respectively. In this embodiment, the outer race 26 is fixed and the inner race 20 is rotatable so that the signal from the rotating inner wire 34 is routed through a rotary electrical transmission device such as a slip ring 40. Fixed output wire 3
8.

FIG. 2 is a block diagram of one embodiment of the measuring device. 3
The output of the MHz oscillator 42 is directly input to the phase detection circuit 44 via the ball pair 22 of the hair ring 10 (first shown). Phase detection circuit 44
measures the phase angle deviation between the output signal of oscillator 42 and the signal from bearing 22 and provides an output signal proportional to the phase angle deviation. The phase angle shift is E) [)
Since it is a function of the capacitance of the bearing, which is a function of the coating thickness, the output voltage from the phase detection circuit 44 is proportional to the EHD coating.

FIG. 3 shows an embodiment of a device implementing the functions shown in FIG. Wire 36 of FIG. 1 connects to the ground side of bearing 10 in the circuit of FIG. 3, and wire 38 of FIG.
is connected to the capacitor.

The difference in phase angle between the high frequency signal from the oscillator 42 and the signal passed through the bearing is caused by the impedance, particularly the capacitance, of the bearing. In Equation 1, the phase angle difference is related to the real and imaginary parts of the impedance.

The imaginary part (ZxMAGtNAny) is related to capacitive impedance, which is the inverse of reluctance.

The real part (ZRIEAL) is the resistive impedance, which mainly consists of a fixed resistor 4 placed in series with the bearing.
6 and also includes the resistance of the bearings.

In FIG. 3, this fixed resistor 46 is shown as a 3 ohm resistor, but in practice may have other values in other applications.

The circuit shown in FIG. 3 is merely an example for carrying out measurements; resistors 46 in the range of 2 to 4 ohms are acceptable in the circuits described above. properties can be supplied.

Other applications, such as roller bearings, use circuits of significantly different dimensions and configurations. 3KH2 is
It is chosen as the oscillator frequency because it is high enough to eliminate distortion and low enough to obtain acceptable gain. To monitor the output of phase detection circuit 44, a voltage monitoring device such as a VOM, strip chart recorder, or oscilloscope may be used.

FIG. 4 is a symbolic representation of the rolling member 22 showing the locations of the major capacitance and resistance values.

FIG. 5 is an equal circuit of all bearings using the symbols shown in FIG. 4 when there are N rolling members.

The phase angle (θ) can be calculated by dividing the impedance of fixed resistor 46 by the total impedance of the bearing in Equation 1. Equations 2 and 3 are representative representations of the impedance of the fixed resistor and the impedance of the bearing, where N is the number of rolling members, ω(
omega) is the frequency of the signal from oscillator 42.

ZRIEAL=R(46)
(EQ2) ZIMAG” (EQ3) Similar to the capacitance between the inner race 20 and the outer race 26, the resistance R between the rolling member 22 and the raceway
o, RI and capacitance Co.

The CI equation varies depending on bearing type, various geometric parameters, cage material (if one is used), lubricant properties, and EHD coating thickness.

The EHD coating thickness measurement technique is useful as an investigation device to measure EHD coating thickness in a variety of control situations, and can also be used to monitor lubrication of working bearings. This data is useful in determining the physical condition of the bearing, the need to add lubricant or grease, or as a lubrication sensor in an active lubrication system. This technique is also used to measure the thickness of coatings in hydrostatic bearings and gases or liquids when applying voltage between moving and stationary members. This acts as a coating/no coating indicator, but does not give data on the amount of coating thickness.

Accordingly, the present invention relates to an apparatus and method for measuring the thickness of an EHD coating on a working rolling member bearing by measuring the capacitance of the bearing, which capacitance occurs between the rolling member and the raceway; The oil film provides high dielectric separation.

The advantage of this capacitance measurement device and method is that the capacitance can be measured in the field of interest, primarily in the field of well-developed EHD films, and that the capacitance is sensitive to very small changes in film thickness. It also changes sufficiently.

The capacitance between the inner and outer races of a working bearing is an exponential function of the coating thickness. The total capacitance is formed as a series of series and parallel capacitors, as shown in FIG. 5, with the oil film being a dielectric and the rolling members and raceway acting as conductive plates. A mathematical model has been developed that relates the thickness of the EHD coating to the capacitance of the bearing. The capacitance of the working bearing is measured by applying a high frequency electrical signal between the inner and outer races of the paired link. The capacitance of the bearing causes a phase angle shift between the output signal from the bearing and the input signal. By measuring this shift, an analog signal proportional to the phase shift is generated. E
A mathematical model in which the HD coating thickness is related to the bearing capacitance and the phase shift due to this capacitance is used to relate the measured phase angle to the actual EHD coating thickness.

As mentioned above, the embodiments have been described, but the present invention can be variously modified within the scope of the idea of the present invention.

[Brief explanation of the drawing]

Figure 1 shows a ball bearing car modified to measure the capacitance of one of the bearings) IJ
2 is a block diagram of an embodiment of the capacitive measuring device, FIG. 3 is a circuit diagram of an embodiment of the capacitive EHD film measuring device, and FIG. 4 is a diagram of each rolling of the bearing. A symbolic diagram showing an embodiment of the electrical circuit diagram of the members, FIG. 5 is a circuit diagram of the entire bearing having N rolling members. 10...Double row ball bearing, 12...War/housing, 188...Shaft, 20...Inner race, 22...Ball e Beary:/ri, 26...
Outer race, 30... Retaining ring, 32... Insulator, 42... Oscillator, 44... Phase detection circuit.

Claims (3)

[Claims] (1) a rolling member bearing device having a relatively rotatable inner race and an outer race forming a raceway therebetween; A device for measuring the thickness of a lubricating film, comprising: a plurality of lubricating rolling members movable within the bearing device; and a device coupled to the bearing device to measure the capacitance of the rolling members. (2) a rolling member bearing having a rotatable shaft extending into the housing; an electrically insulated inner race rotatably engaged to the shaft within the housing; an electrically insulated fixed outer race forming a raceway with the inner race; a plurality of rolling members movably mounted within the raceway; and a device coupled to the bearing for measuring capacitance of the bearing. A lubricating film thickness measuring device comprising: and. (3) providing an electrical signal to a rolling bearing member; and measuring a capacitance of said rolling bearing member, said rolling bearing member being relatively rotatable forming a raceway therebetween; It has an inner lace and an outer lace,
Multiple lubricating rolling wheels movable within the raceway.
A method for measuring the thickness of a lubricating film in a rolling bearing member device equipped with a bearing member.